1. Field of the Invention
The invention relates to a steering device for steering a moving body, a moving body having the steering device, and a steering method of steering the moving body.
2. Description of the Related Art
There is a conventional circular steering device (handle) used in a general vehicle as a steering device for controlling the direction or amount of movement (speed, acceleration) of a moving body. This steering device not only determine the amount of movement in relation to the amount of operation carried out by an operator, but also determines the direction of movement of the moving body based on a steering direction. Such a circular steering device is connected directly to a steering rack by means of a mechanical link so as to convert a circular operation of the steering device to a linear motion. Therefore, this steering device is restricted in term of the design, as it has to be provided with sufficient rigidity and designed with safety in mind when incorporated into a vehicle.
Therefore, as a steering device for use in operating small vehicles such as a wheelchair and a cart, a work machine and the like, a steering device that has a simple structure in terms of its operability and internal space is often used. Specifically, there is generally known a joystick steering device for operating a rod-like lever or hand rim-like operating element to perform steering. Such a joystick steering device is disclosed in Japanese Patent Application Publication No. 2005-306184 (JP-A-2005-306184), Japanese Patent Application Publication No. 8-281584 (JP-A-8-281584), and Japanese Patent Application Publication No. 2000-60904 (JP-A-2000-60904).
For example, the steering device disclosed in JP-A-2005-306184 is configured to detect right and left steering angles of a joystick operated by an operator, controls a drive amount of a wheel in accordance with the detected steering angles, and applies a steering reaction force to the joystick in accordance with the detected steering angles. Accordingly, a moderate resistance is applied to a return operation when returning the joystick, so that the operator can perform a delicate operation as intended when returning the joystick.
The steering device disclosed in JP-A-8-281584, which is used in a measuring device or a working machine, a certain range of the amount of operation of the joystick is considered a dead zone on software. As a method of determining the width of the dead zone, this invention uses a method of sampling, in a certain sampling cycle, a voltage signal that is output in accordance with a swing angle of the joystick, comparing a changing quantity of the voltage signal per sampling cycle with a predetermined threshold value, and neglecting the dead zone when the changing quantity exceeds the threshold value.
The invention disclosed in JP-A-2000-60904 describes a steering device used in an electric wheelchair. In this invention, right and left hand rims are used as a steering device in place of a joystick steering device to control wheels of the wheelchair by rotating these hand rims. Accordingly, the operability for controlling the moving speed and the like can be enhanced.
However, each of the technologies disclosed in these publications is used for determining the amount of movement in relation to the amount of operation performed by the operator, and therefore it is not necessarily true that the movement is controlled by an intuitive operation performed by the operator.
Therefore, considered is use of a steering device that is capable of controlling a movement based on a force applied by an operation of an operator and thereby controlling a movement of a moving body by performing an intuitive operation. However, the problem of such a steering device is that, in spite of its high responsiveness for promptly responding to the force applied by the operator, it is difficult to perform a delicate operation for controlling a direction and an amount of movement.
Thus, if the dead zone is set large in relation to the force applied by the operator, the responsiveness for eliminating a response to an applied small force is degraded, but at the same time when the dead zone is set low, sufficient operability cannot be achieved.